Whats the inflation rate on fiat currencies 
I think it depends on the currency. Try googling it, there should be a lot of results.Meant in the case of a currency collapse or high inflation bitcoins will hit 1K pretty dang fast relative to any one currency
I would still be difficult for all currency pairs to collapse in unison. Governments own a lot of fiat currency (not just their own) and will always need to exchange this currency reserve for there own currency. In this way a lot of value can move between fiat currency pairs. So it is relative and not all pairs can devalue unless Governments decided to hold Bitcoin as a reserve currency (not impossible buy unlikely).